Two gameplay issues:
One: altering attributes and health/resolve
Powers or drawback/limits that change attributes (such as alternate form, signature item) don't specify wether they also change derived stats like health or resolve. Monster Girls QS stats seem to imply that they do. If so, there is no guidance as to how damage and stress transfers. With the MG example, her troll form has 12 health. She takes 6 damage and transforms. Does her human form now have 6 or 0 health?
This question is particularly important as most combat will happen in the form with higher stats, so transferring healthvalues needs to be cleared up.
Two: has been covered a bit already: Sorcery is too powerful and unfun as it is. A power that can imitate any other power is incredibly useful, and the limitations (quick action, presence test) aren't significant enough. I recommend adding a further limitation in that you aren't allowed to activate more than one sorcery power at once - so if you activated blast and want to fly now, you need to drop blast (and spend another quick action to regain it). This avoids broken combinations and incentivises players to invest in "normal" powers they regularly use. To allow some more flexibility, the signature power boost could be replaced with a prepared spell boost that allows two concurrent powers (this would shift signature powers to being covered by normal, non-sorcery powers, and free up a bit of space to avoid major layout changes)